The particulars of radioactive contamination of concrete wastes by 137 Cs were studied. x-Ray phase analysis and chemical analysis show that clayey materials, including Al 2 O 3 , Fe 2 O 3 , K 2 O, and MgO, on which 137 Cs sorption is possible, were present in the concrete wastes. The content and form in which 137 Cs was found in radioactive concrete wastes from nuclear power facilities as well as in model samples were determined. When the wastes were treated with nitric acid the binder dissolved and a polydisperse suspension formed. The suspension consisted of three phases: solution, fine suspension, and rapidly settling precipitate of heavy filler particles. x-Ray phase analysis was performed and the 137 Cs mass ratio and distribution in the phases were determined. The possibility of decontaminating the concrete by a reagent method was evaluated.Large amounts of radwastes, a considerable fraction of which consist of concrete structures, are inevitably produced when nuclear power facilities are decommissioned. There are many known methods for decontaminating concrete. Usually, concrete structures are decontaminated by mechanical removal of the surface layer using different equipment, as a result of which secondary wastes in the form of fragmented concrete are formed [1]. Ordinarily, such wastes are conditioned by incorporation into cement prepared using liquid radwastes [2] or by saturation with a highly penetrating cement solution [3]. As a result, the volume of the cemented radwastes and correspondingly the storage costs increase.As a rule, concrete wastes are classified as medium-and low-level. 137 Cs is one of the main contaminating γ-and β-emitting radionuclides. Its half-life is about 30 years, so that cool-down of the wastes to lower the activity to a safe level is of little use and in many cases removing this isotope from concrete will make it possible to remove such wastes from the radwaste category.The objective of the present work is to assess the possibility of volume 137 Cs decontamination of fragmented concrete wastes. Concrete is a nonuniform composite material, so that to develop a method of decontamination it is necessary to study the form in which the radionuclides, specifically, 137 Cs, are found in the wastes.The objects of study were concrete wastes from the rehabilitation of radiologically hazardous facilities: sample 1 -a 25-kg concrete block with γ-ray dose rate 0.1 m away from the surface to 500 μSv/h and sample 2 -fragmented wastes with γ-ray dose rate 0.1 m from the surface not exceeding the background level. In addition, model samples obtained by contaminating clean concrete with a radioactive solution as well as by cementing a radioactive solution were studied.For γ-spectrometric analysis, the waste fragments were comminuted and average samples were taken. The samples were subjected to radiometric analysis performed using an ORTEC-GEM 35P (Finland) automated four-channel gamma spectrometer with a semiconductor detector in the central laboratory of the Moscow Scientific and Industria...

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This paper presents data on lithological composition, distribution, reservoir properties, geochemistry of organic matter and genesis of carbonate rocks of the Bazhenov formation within the central part of Western Siberia (the region of the Khantei hemianteclise). The following types of carbonates are distinguished: a) primary biogenic – shell rock interlayers and residues of coccolith; b) dia- and catagenetic – in varying degrees, recrystallized rocks with coccoliths, nodules and aporadiolarites; c) catagenetic – cracks healed with calcite in limestone of the foot of the Bazhenov formation. It was determined that the crystallization of the carbonate material of nodules took place in various conditions: in the bottom part of the sediments and in the later stages of diagenesis. The source of calcite for nodules was calcareous nanoplankton or bivalve shells. The carbonate content of the cuts decreases in the following sequence: Yuzhno-Yagunsky → Povkhovsky → Novortyagunsky → Druzhny areas, which are associated both with facial features and various physicochemical conditions of diagenesis and catagenesis. Transformation of organic matter increases in the northeast direction from South Yagunsky to Povkhovsky area, which is confirmed by molecular parameters of catagenesis. The carbonate rocks of the bottom part of the Bazhenov formation in the South Yagunsky area are similar in structure to the main oil-bearing reservoirs of the Salym and Krasnoleninsky fields.

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A substantial quantity of solid radwastes consists of contaminated building materials, primarily, different grades of concrete. The largest amount of concrete arises during decommissioning of objects of nuclear power and radiochemical enterprises which have outlived their service life, are unprofitable, or do not meet modern safety requirements [1]. To make these objects radiation-safe, building structures must be completely or partially disassembled, primarily by mechanical methods (explosions, breaking or sawing into pieces, and so forth) [2]. This debris ranges in size from dust particles to pieces with mass up to hundreds of kilograms and is placed in special long-term storage (burial) sites. Since it is expensive to build and service such sites, it is economically desirable to develop technologies that decrease the volume of the wastes which are to be stored for a long time (buried). According to OSPORB-99 [1], building materials from which radionuclides have been removed are largely low-level wastes and accordingly need not be classified as radioactive wastes.Radioactive building materials which are contaminated with long-lived α emitters present the greatest danger. The most stringent norms have been established for them -these materials are considered to be radioactive when their content of uranium or transuranium elements ranges from 1 kBq/kg and higher for 226 Ra (in equilibrium with the decay products) to 10 kBq/kg and higher [1]. For materials contaminated with radionuclides with a long half-life, the method of delayed disassembly or cool-down to allow the activity to drop to acceptable levels is unacceptable, which makes the problem of handling such materials of great current interest.Our objectives in the present work were to study the particularities of the contamination of real concrete wastes by uranium isotopes and to develop a method for decontaminating such wastes.Real radioactive concrete wastes from the research center and an industrial enterprise of the nuclear fuel cycle were the object of the present investigations (Fig. 1). The wastes were represented by debris containing residues of the binder (Fig. 1a) and fragments of a thin-wall (35 mm thick) reinforced concrete structure with two plane-parallel boundaries (Fig. 1b). For radiometry and radiochemical analyses, the waste fragments were ground and medium samples were taken. The analysis was performed in the central laboratory of the MosNPO Radon, which is accredited in the system of radiation-monitoring laboratories. x-Ray phase analysis of the waste samples was performed with a DRON-4 diffractometer which automatically recorded the diffraction pattern in steps using filtered FeK α radiation. A binder fraction with particle size less than 2.5 mm was sieved to investigate the concrete sample (see Fig. 1a). The x-ray phase analysis data show that CaCO 3 (calcite), SiO 2 (α quartz), 3CaO·Al 2 O 3 ·CaCO 3 ·12H 2 O, 4CaO·Al 2 O 3 ·13H 2 O are present in the binder fraction. The radionuclide composition of the binder is represented by 234,235...

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This paper addresses potential application of data on stable carbon and oxygen isotope composition of carbonates for study of organic rich source rocks on the example of the Late Jurassic–Early Cretaceous Bazhenov Formation (West Siberian petroleum basin, Russia). Geochemical studies were conducted for sections located in central (most productive) and peripheral (northern and southern) regions of the Bazhenov Formation distribution area, containing deposits formed under different conditions. We identified key factors impacting stable isotope composition of carbonate minerals and established relation of their isotope composition to the formation conditions. Using a thermodynamic model of carbon and oxygen isotope exchange in the carbonate–water–carbon dioxide system, it is shown that variations in the isotope composition of secondary carbonates are affected by isotopic composition of primary carbonates in sediments and by the isotope exchange reactions with water and carbon dioxide, generated during the source rocks transformation. Our results demonstrate that stable isotope data for carbonates in the Bazhenov Formation together with standard geochemical methods can be efficiently applied to determine sedimentation conditions and secondary alteration processes of oil source rocks.